In general, gliding boards have a core which is made either as a prefabricated element or by using injection and molding operations, during which chemical components are introduced into a mold and react so as to expand in order to form the core in situ. More precisely, this expansion takes place in the volume defined between two outer layers, an upper one and a lower one, which respectively form the protective upper layer of the board and the gliding surface, as well as lateral reinforcing elements that form some or all of the edges. During the injection, and the expansion which follows, these various elements are pressed against the cavity and the lid of the mold.
In general, the mechanical properties of injection-molded skis are directly linked with the use of internal reinforcements, which generally have a high rigidity. This type of reinforcement is generally made either of metal or based on fiber materials, and especially using laminates that may be based on glass fibers. The choice of the materials, as well as the dimensions of the reinforcement and the way it is positioned inside the core, are crucial for obtaining the desired mechanical characteristics.
As the core expands, it pushes outward all the elements contained in the volume that it fills. All the substantially flat reinforcements known to date are generally arranged either in contact with the layer that forms the gliding surface or the protective upper layer, optionally with the interposition of other specific reinforcements. In order to ensure that the reinforcement is positioned correctly during the injection operation, it is generally adhesively bonded beforehand onto the outer layer with which it comes in contact, which prevents this reinforcement from being displaced when the polyurethane foam moves.
A problem arises with gliding boards whose upper face is not strictly flat, but instead includes recesses or other protuberances. This is because, in this case, it is not possible for the rigid reinforcement to deform in order to adopt the outer shape of the board. A solution to this problem has been proposed by the Applicant in document FR 2 818 915. This solution consists in making openings inside the rigid reinforcement, in order to allow the protective upper layer to be deformed according to the desired volume but without excessively deforming the reinforcement itself. These openings may be complete openings, hence making it easy for the polyurethane foam to pass through. These openings may also be partial openings, so as to allow local deformation of the reinforcement which remains adhesively bonded under the protective upper layer.
These solutions have some drawbacks, however, since it is difficult to accurately limit the passage of the foam that constitutes the core. This sealing problem compromises the precision with which the shapes can be reproduced. Moreover, these solutions require the reinforcement to be located immediately below the protective upper layer. It may prove beneficial to position the reinforcement at an intermediate height, however, rather than directly below the protective upper layer or directly above the gliding surface.
Another solution that makes it possible to distance the reinforcement from the outer layers, which is proposed by document FR 2 312 273, involves perforating the rigid reinforcement over its entire surface in order to let the foam pass fully through. This solution has the drawback that making openings in the reinforcement inevitably causes an at least local reduction in the stiffness of the reinforcement. In the case of fiber reinforcements, the cutouts made in the reinforcement hence destroy the continuity of certain fibers, and therefore reduce the overall strength of the reinforcement.
It is an object of the invention to be able to use reinforcements whose height is optimized in order to provide the board with a specific stiffness. It is also an object to let the reinforcement retain its intrinsic properties, so as to influence the stiffness of the board in the desired way.